Quasi-static crushing behaviors and plastic analysis of thin-walled triangular tubes

• Triangular tubes have three crushing modes divided by two critical base angles.
• The crushing mechanism includes six plastic hinges and one traveling plastic hinge.
• An efficient plastic analysis model was built to predict the mean crushing force.

To study the collapse mechanism and energy absorbing ability in lateral compression, metallic isosceles triangular tubes were designed and fabricated, with the base angle varying from 30°, 45°, 60° to 75°. According to the experiments, it is found that three typical crushing modes and two critical base angles characterize the lateral crushing behaviors of the isosceles triangular tubes. Tubes with base angle smaller than 45.6° are crushed without obvious fold. Tubes with base angle greater than 72.6° have side-wall contact at the buckling center before forming a new shortened triangle and being folded. With the base angle between these two critical values, tubes behave the same as the equilateral triangular tube. Triangular tubes have unified energy absorbing mechanism, including six plastic hinges and one traveling plastic hinge. The mean crushing force of the tube was well predicted based on plastic analysis, supplying criterion for material selection in designing anti-impact structures.